Got some time and tested that approach with ST7920. And it indeed works.
While PBP seems to beginning to belong to dead language category, I'll leave this simple code here anyways - maybe someone will find it useful.

ST7920 is wired as standard HD44780 in 4 bit mode. With appropriate LCD pins defined.

Code:
LCDOUT $FE,$2E 'enable graphic mode
LCDOUT $FE,$80 'set Y position to zero (Top)
LCDOUT $FE,$80  set X position to zero (Left)
LCDOUT 255 'draw a line consisting of 8 pixels in top left row
Note: X counter increases after each write by itself, but Y counter - not, so you have to do it manually.

And this simple code fills up entire screen with white:

Code:
LCDOUT $FE,$2E
for Z=0 to 32
LCDOUT $FE,$80+z
LCDOUT $FE,$80
FOR x=1 TO 18
LCDOUT 255
NEXT
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